The Influence of Backwater Al3+ on Diaspore Bauxite Flotation

The effect of Al3+ in backwater on the flotation of diaspore bauxite was investigated by micro-flotation tests and the underlying mechanisms were investigated by inductively coupled plasma (ICP) measurement, zeta potential measurements, solution chemistry analyses, and synchrotron near edge X-ray absorption fine structure (NEXAFS) analyses. The ICP measurement results show the concentration of Al3+ in backwater was up to 1 x 10(-4) mol/L. The micro-flotation results indicated that backwater Al3+ reduced the flotation recovery of diaspore and improved the flotation recovery of kaolinite at pH 9, which was the pH value used in the industrial flotation. The adsorption of Al3+ species changed the zeta potential, the Al atomic abundance, and the number of active sites on the mineral surface. In particular, the result of solution chemistry analyses and synchrotron NEXAFS analyses show that the Al3+ in backwater was adsorbed on the mineral surface in the form of Al(OH)(3) (s), and the bond of -Al-O-Al-(OH)(2) or -Al/Si-O-Al-(OH)(2) was formed at pH 9. It changed the intensity of hydrogen bond force between minerals and collectors, and resulted in the depression of diaspore flotation and the activation of kaolinite flotation. This study can be used to guide the application of backwater in the flotation of diaspore bauxite in industry.